Fairfax Town Hall Rain Garden

Acknowledgments: This project was designed and installed in 2010 as part of the 10,000 Rain Gardens Project. Special thanks to the Town of Fairfax, Sustainable Fairfax, Permaculture Marin and workshop participants who helped make this project possible.

Interpretive sign at project site

Project Overview

The project site at Town Hall is centrally located between a vibrant downtown and popular bicycle and hiking trails. Adjacent to the town pavillion and a public park that are used actively, including a summer-long weekly farmers market and several annual festivals, the site is highly visible and thousands of people will pass by it each year. Town staff helped to identify this location recognizing the potential for it to be transformed into a cost-effective demonstration of rainwater harvesting with immediate positive impacts. A presentation was made to Town Council for approval.

Rain Garden Unique Features

The rain garden was designed and installed to demonstrate a simple and effective solution to stormwater mitigation and water conservation. Roof water from Town Hall discharges directly into Fairfax Creek and this rain garden will act as a buffer for a portion of the building's roof area. There is enough capacity to handle the smaller, more frequent storm events of up to one inch of rainfall. With a chance to slow down and soak into the ground, this stormwater is turned into a resource to support appropriate plantings. A mulch-filled basin acts as a sponge to hold moisture longer into the dry season, and feeds healthy living soil. The combination of mulch, healthy soil, and plants helps biologically filter the water while also decreasing the demand for irrigation and improving plant health.

Section view of rain garden - Design by Jeffrey Adams

Bottom of downspout and new pipes

Rain events that exceed the capacity of this rain garden overflow via a pipe back to the original drain.

The downspout was disconnected from the existing drainpipe and adapted to a pipe that conveys the water 10 feet away from the building's foundation to the rain garden. Due to the constraints of this particular site, a second pipe was installed as an overflow back to the existing drainpipe to provide a safe place for water to go in the event of a storm that exceeds the rain garden's capacity to hold, infiltrate, and evapotranspire.

The size of the rain garden was constrained by an underground utility line, and the adjacent creek and public pathway. To identify the location of all underground utility lines, USA Dig (www.usanorth.org) came out to the site. This project was implemented by sixteen participants during a hands-on workshop offered by 10,000 Rain Gardens Project staff.

The area of the rain garden was laid out and the existing mulch was pulled to the side for later use. The basin was dug to a maximum depth of 18 inches and the excavated soil was used to create a berm.

Mulch is scraped away to prepare the site

Volunteers dig rain garden basin and build berm

A load of wood chips was provided free by the Town. The basin was filled with wood chips to increase water retention and promote soil building. Low water-use native and Mediterranean adapted plants, including Yarrow, Sage, Coffeeberry, California Buckwheat and Red Fescue were planted on the berm, and rushes were planted in the basin. All the new plants, as well as surrounding established vegetation will benefit from the increased available water in the soil and provide aesthetic interest and wildlife habitat. Organic compost was spread around the new plants and a thick layer of wood chips was applied as mulch. These plants will establish quickly and need only occasional hand watering during the first one to three years of establishment. No irrigation system was installed on this project.

System Costs

Plants:Compost:Pipe and fittings:

$240.00$50.00$50.00

Approximate total costs: $340.00

System Operations and Maintenance

Add wood chips as needed to maintain mulch

Inspect inflow and overflow to remove any potential blockages and as needed after large storm events

Weed quarterly or as needed

Hand water during first summer to establish plants (monthly or as needed per weather)